Cystic Fibrosis Flashcards
What is the mode of inheritance for CF?
Autosomal recessive
What is the most common mutation leading to CF?
Delta F508 (deletion of codon 508) ---> deletion of 1 aa (Phe) (chromosome 7)
Therefore not causing a frameshift
What are some ways of screening for CF?
Foetuses: Chorionic Villus Sampling or amniocentesis
Infants: Guthrie test
What is the normal function of the CFTR protein at mucous membranes?
Cl- is transported in the cell and Na+ out of the cell by antiport exchange on the basal membrane (normal electrochemical gradient of the cell)
c.AMP stimulates active transport of Cl- through the CFTR on the apical membrane.
Cl- active transport out of the cell closes ENaC channel, so Na+ does not re-enter the cell
This means that more NaCl enters the mucus, causing water to move out of the cell by osmosis, so the mucus is watery enough to be moved.
What does the defective/absent CFTR result in at mucous membranes?
Prevents active transport of Cl- out of cells.
Na+ & H2O remain in cells
What is the normal function of the CFTR protein at sweat glands?
Na+ and Cl- diffuse into the sweat in the sweat gland from the blood, and consequently H2O follows.
Na+ and Cl- are reabsorbed back into the bloodstream through separate channels.
The sweat is not too salty (high water:salt)
What does the defective/absent CFTR result in at sweat glands.
Na+ and Cl- not reabsorbed from the sweat.
High amount of NaCl in sweat (“salty sweat”)
Low water:salt ratio
What is the consequence of the thick, hardened mucus at mucous membranes in CF patients?
Muco-ciliary escalator cannot function, therefore trapped dirt and pathogens are not cleared —> frequent lung infections
Mucus blocks pancreas, preventing digestive enzymes (especially lipases) from reaching the intestines —> malabsorption of fats —> fatty stools (steatorrhoea)
Why are 95% of male CF patients infertile?
Congenital bilateral absence of vas deferens (sperm not transported into seminal vesicles)
note: sperm still produced
Name some respiratory complications of CF.
- breathlessness
- nasal polyps
- haemoptysis (coughing up blood)
- spontaneous pneumothorax
- respiratory failure
What are the most common pathogens involved with CF lung infections?
- Pseudomonas aeruginosa
- Haemophilus influenzae
- Staph.
Apart from the Guthrie test/sweat test, how else could you diagnose CF?
Test fat composition of stools to confirm steatorrhoea
Look for clubbing (acopaquia) —> excess tissue growth causing swelling of the fingers
What is the prophylactic (conservative) treatment for CF?
Physiotherapy & breathing exercises (aids breathing by mobilising mucus)
Prophylactic antibiotics to limit infections
What is the therapeutic (medical) treatment for CF?
Bronchodilators = aid breathing and lower infection risk
Lipase supplements (aid fat digestion)
Fat soluble vitamin supplements (ADEK)
DNAse aerosol spray (breaks down DNA of lysed white blood cells —> reduces stickiness of mucus)
What is the surgical treatment for CF?
Double lung transplant (replace damaged lungs)
